鄂尔多斯盆地南部长6段储层成岩作用特征

Diagenetic features of reservoirs in the Chang-6 member, south Ordos basin

为评价和预测鄂尔多斯盆地上三叠统延长组长6段低渗储层,根据岩石薄片、铸体薄片、扫描电镜等资料对长6段储层进行了分析研究。结果表明:①长6段砂岩在该盆地北部具"高长石、低石英"、南部具"低长石、高石英"特点,分选性较好、磨圆度较差;②主要建设性成岩作用为溶蚀作用、环边绿泥石形成、烃类侵位作用及高岭石化作用等,压实作用强烈是导致该储层早期砂岩孔隙丧失的根本原因,胶结作用是造成后期储层岩石致密的主要因素。在此基础上,进一步分析了鄂尔多斯盆地南部的成岩作用演化序列。

The low permeability reservoirs in the Chang-6 member of Upper Triassic Yanchang Formation in the southern Ordos basin were evaluated and predicted by using rock thin section, cast thin section and SEM data. The following understandings were obtained. The sandstones of the Chang-6 member are characterized by 'high content of feldspar and low content of quartz' in the northern part of the basin, while by 'low content of feldspar and high content of quartz' in the southern part of the basin, and show relatively good sorting but poor psephicity. The main types of constructive diagenesis include dissolution, rim chlorite growth, hydrocarbon emplacement and kaolinization. Strong compaction is the fundamental factor resulting in the loss of the pores in sandstones in the early stage, while cementation is the major factor causing the tightness of reservoir rocks in the later stage. In addition, the evolutionary sequence of diagenesis in the southern part of the basin is also discussed based on the above study results.